Brush for dynamo-electric machines and motors



(No Model.)

J..-;, P. B. FISKE. BRUSH FOR DYNAMO ELECTRIC MACHINES AND MOTORS. N01 501,060 Patented July 11, 1893.

UNITED STATES PATENT OFFICE.

JONATHAN P. B. FISKE, OF LYNN, ASSIGNOR TO THE GENERAL ELECTRIC COMPANY, OF BOSTON, MASSACHUSETTS.

BRUSH FOR DYNAMO-ELECTRIC MACHINES AND MOTORS.

SPECIFICATION forming part of Letters Patent No. 501,060, dated July 11, 1893. Application filed January 31, 1893. Serial No. 460,225. (No model.)

To aZZ whom it may concern: cumulative one and the carbon brush may be- Be it known that I, JONATHAN P. B. FIsKE, come practically useless as a current collecta citizen of the United States, residing at ing device on account of the roughness of the Lynn, in the county of Essex and State of Mascommutator surface. 55 sachusetts, have invented certain new and My invention aims to obviate this trouble useful Improvements in Brushes for Dynamoby placing the copper brush and the carbon Electric Machines and Motors, of which the or other high resistance brush on different following is a specification. wearing surfaces of the commutator or upon My invention relates to improvements in different commutators connected to the same 60 1o brushes for dynamo electric machines and armature coil or coils, so that the two brushes motors. It is intended particularly for use or the compound brush, copper and carbon, with direct current machines, that is, electric have independent bearing points upon the machines generating or receiving electric curcommutator. rents which are commuted so as to flow in one The invention comprises broadly, a compos- 65 direction. ite brush for electric machines consisting of The object of the invention is to enable eleca low resistance conductor, and a relatively tric currents to be taken up from the commuhigher resistanceconductor,havingindependtator or delivered to it without the occurrence ent bearing surfaces on a commutator, said of sparking orflashing between the segments. high resistance conductor or brush being 70 Such sparking is very apt to occur when the placed slightly in advance of the low resistpotential difference between the adjacent segance conductoror brush so that the short cirments is considerable, or when a large volume cuit through the coil or coils undergoing comof current is flowing, and it destroys or inmutation shall be broken through said high jures thecommntatorsurface. Manyarrangeresistance brush or conductor. 75 2 5 ments have been devised in the past for over- In the drawings Figure 1 shows a commucoming this difficulty, one of the best of which tator provided with two brnshesin accordance is the use of a carbon brush which on account with my invention. Figs. 2, 3 and 4: show of its relatively high specific resistance premodifications. Vents the flow of very heavy currents when The invention may be carried out in a num- 8o an armature coil is short circuited under the her of different ways.

brush. On account of its relatively high re- In Fig. 1 a copper brush A and a carbon sistance, however, the carbon brush is only brush B are placed side by side and are conadapted for use with machines using currents nected to one of the terminal wires loading of rather high potential, say about two hunfrom the machine. The carbon brush, or 85 dred volts, and when heavy currents are to be brush of highest resistance, is placed slightly transmitted a large commutator is required in advance of the copper brush in the direcowing to the limited current capacity of the tion of revolution so that the segment concarbon brush. To overcome these difficulties nected to the armature coil in which the cur copper and carbon brushes have been comrent is being reversed leaves this brush last. 0 4o bined into a compound brush or composite The opposite wire of the circuit is connected brush and used together on the commutator, similarly to brushes upon the other side of and copper brushes have been arranged to the commutator 0. Any slightsparkingattho form receptacles for carbon brushes so that copper brush which might cause roughness of the carrying capacity of the copper and the the commutator can, as is evident, have no in- 5 spark preventing properties of the carbon fluence upon the carbon brush in such an armight be utilized. Such arrangements while rangement, as the carbon bears upon a differthey work well at first soon give trouble, for ent portion of the commutator surface. the reason that slight sparking at the copper In Fig. 2 the relative lead of the carbon or brush producesaroughness of the commutator high resistance brush over the copper brush 100 surface and the contact with the carbon brush is obtained by placing the commutator se is thereby impaired. The trouble is an ac ments themselves at an angle to the shaft.

This is not a good mechanical construction, however, and is merely introduced as showing a possible modification of the invention.

In Fig. 3, twin commutators are shown one at each end of the shaft and their correspond-- ing segments are connected to the same coils upon the armature. The carbon brush may be placed slightly in advance of the copper brush, as indicated by the dotted line X, or the segments of the commutator at the righthand side of the armature may be given a slight lead over those of the commutator at the left-hand side of the armature.

In large machines a number of copper brushes and high resistance brushes, such as carbon, may be placed side by side or alternately, as shown in Fig. 4, or the copper brushes may be placed nearest the armature and the high resistance brushes farthest therefrom, if desired.

In each case, as represented by the above figure, the effect is the same. The arrangements, Figs. 1 and 4, are the preferred ones, though that of Fig. 3 may be found useful for certain purposes.

WVhat I claim as new, and desire to secure by Letters Patent, is

1. A composite brush for dynamo electric machines, consisting of a low resistance conductor and a relatively high resistance eonductor, bearing upon ditferent portions of the length of the commutator, and so arranged that the high resistance conductor is the last to leave the commutator segment, substantially as set forth.

2. A composite brush for dynamo electric machines, consisting of a low resistance conductor and a relatively high resistance conductor, the latter being slightly in advance of the former, and the two conductors arranged to bear upon different portions of the length of the commutator substantially as described.

3. The combination with a commutator of two or more brushes of relatively high and low resistance, bearing upon different portions of the commutator segment, the brush nearest the armature being of low resistance, substantially as described.

at. The combination with an armature having one or more commutators, of brushes of relatively high and low resistance, arranged to bear upon such commutators in different longitudinal positions, the short circuit between adjacent commutator segments being broken through the high resistance brush, substantially as described.

In witness whereof I have hereunto set my hand this 27th day of January, 1893.

JONATHAN P. B. FISKE.

WVitnesses:

JOHN W. GIBBONEY, BENJAMIN B. HULL. 

